Hi
(named entities) are considered to be a thing of the past. I have been using for some years without any problem their utf-8 equivalent, which is \u00a0 or (this is Sigil's choice) & # 1 6 0 ; without the spaces
I also use "fines insécables" (nnbsp) with their utf-8 value without problem, provided the embedded font recognizes this utf-8 character.
You can find one EPUB3 here which displays fine on Koreader and makes use of both.
https://www.mobileread.com/forums/sh...86&postcount=3
I can provide you regex to perform this change if need be.